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Title: Preparation and characterization of organic silver based conductive inks for flexible electronics
Author: Yang, Wendong
ISNI:       0000 0004 8499 0418
Awarding Body: Heriot-Watt University
Current Institution: Heriot-Watt University
Date of Award: 2019
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Flexible electronics is of considerable interest for many applications due to the distinctive features of low-cost, flexibility and light weight capabilities. However, in translating the technology from research to practical applications there are several challenges. One of them is to formulate suitable ink materials. Organic silver ink, also known as particle free ink, has attracted great interest due to their flexibility in preparation, excellent stability and a relatively low sintering temperature (150~200°C) in comparison with nano silver ink. Although various kinds of organic silver inks have been created, they are still not ideal due to the low throughput, the complex synthetic process, and high temperatures for conductivity near bulk silver (generally > 150°C). Therefore, it has been necessary to develop new types of low-temperature sintering organic silver conductive inks using simple procedures for practical applications on flexible substrates such as polymer films. The aim of this thesis was to develop novel, low-temperature sintering (≤150°C) and highly conductive (near bulk silver) organic silver based inks using simple procedures for flexible electronics and study their properties and application. Three strategies were adopted to develop such inks. The first was to synthesize an organic silver/rGO hybrid ink. The second was to develop novel organic silver precursors with desirable electronic and thermal properties to formulate such inks. The third was to optimize the properties of the formulated inks. Three types of highly conductive organic silver-based inks, silver/rGO ink, silver citrate ink and silver oxalate ink, were developed by using a facile, high yielding and environmentally friendly procedure respectively. The chemical reaction mechanisms in the ink formation and the film formation process were studied in each case. The effects of sintering parameters such as temperature and time on the microstructure and electrical properties of the films have been investigated in detail. In the case of Ag/rGO ink, a remarkable improvement in conductivity was observed, which was attributed to the role of rGO platelets. In the case of silver citrate ink, defects such as the coffee ring effect were eliminated by using solvents containing active components. An optimal silver oxalate ink was formulated finally for a simple circuit application, producing silver films with good quality and favorable conductivity at a sintering temperature of 150°C.
Supervisor: Wang, Changhai ; Arrighi, Valeria Sponsor: Engineering and Physical Sciences Research Council (EPSRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available